Question:
Are you allowed to have security cameras running on Shabbos?
Either constantly recording everything, or just recording based on motion detection (when the camera detects motion, it records)?
Answer:
Generally the cameras are intended to record thieves or other illegal activity. As long as the average person walking by has no intent or interest in being recorded, they may be left on. The screen which plays the video inside one's home should also be turned off on Shabbos if possible, so that he too has no interest in viewing the screen to see who is knocking, watching children playing etc., while it can still record to catch any suspicious activity.